The present invention relates to liquified petroleum (LP) gas fuel system for internal combustion engines, and more particularly to a dual fuel system permitting to run an internal combustion engine at will on LP gas or on conventional liquid fuel, such as gasoline.
The air pollution problems inherent in the operation of gasoline fueled and diesel-oil fueled internal combustion engines are well known. Although various emission control devices have been used in the past and are presently in use, and although emission control devices are required by federal legislation and regulations to reduce the amount of pollutants discharged in the atmosphere by internal combustion engines, emission control devices are not entirely satisfactory, they are subject to deterioration with the passage of time, and they are often a hindrance preventing the internal combustion engine from operating at best efficiency and at an economical fuel consumption rate.
Liquid fuels, other than gasoline and diesel fuel, have been proposed for the purpose of reducing consumption of fossil fuels and of decreasing the quantity and the toxicity of the pollutants discharged in the atmosphere. Natural gas and LP gases, such as porpane and butane, have also been proposed as a replacement for conventional liquid fuels such as gasoline, for the purpose of reducing atmospheric pollution, decreasing the operating costs of internal combustion engines, as compared to the costs of operating on gasoline, and the volume of contaminant emission, as compared to gasoline, without complex emission control devices, or for the purpose of entirely eliminating emission control devices. The use of natural gas as a fuel for internal combustion engines is convenient for stationary engines, such as pipeline compressor engines, engines used in oil field operations, water pumping, or production of electricity, for example. However, the use of natural gas as a fuel for internal combustion engine mobile installations, such as in motor vehicles and the like, presents many inconveniences as natural gas must be compressed in thick-walled tanks at a very high pressure, and a battery of a plurality of relatively small high pressure tanks is required for providing a motor vehicle with a reasonable range between refueling stops. Furthermore, natural gas compressor stations are not readily available to the average motorist.
The use of LP gases, such as butane and preferably propane, presents many advantages over the use of natural gas for fueling internal combustion engines. For example, propane is in a liquid phase under a relatively low pressure at room temperature and requires only thin-walled tanks for safe containment. Many systems using LP gases for fueling internal combustion engines have been proposed and some are presently in use in particular applications such as for service trucks, small tractors, lift trucks and the like, in manufacturing plants and in mines, and for fueling motor vehicles operated by LP gas producers, distributors and dealers.
An example of LP gas fuel systems for motor vehicles is disclosed in U.S. Pat. No. 2,855,759, and diverse dual fuel systems have been proposed to permit conventional internal combustion engines to run on a gaseous fuel, or to run at will on a gaseous fuel or on a liquid fuel such as gasoline, as desired, as disclosed for example in U.S. Pat. Nos. 4,056,087 and 4,063,905 and in Popular Mechanics of September, 1979 (page 48) and April, 1980 (pages 108-109, 201). In heretofore known LP gas fueling systems or dual fuel LP gas and gasoline systems, whether the LP gas is supplied from the LP gas tank in a liquid or in a gaseous phase, complete dual fuel mixing systems are required, thus necessitating the replacement of the conventional gasoline carburetor by an LP gas mixer, or by LP gas mixer and gasoline carburetor combined in a single unit or, in the alternative, by mounting a complex gas mixer at the inlet of the carburetor or in the form of a flange adapter between the carburetor and the engine inlet manifold.